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Foundation Systems - Concrete, RapidGrid and RapidPad

A strong foundation is important when siting a garden building.


Dunster House would recommend a flat, level concrete base. If you are unsure about building your concrete base we would recommend that you consult an experienced tradesman. Please note that the base needs to be level with no run off, the building will provide this. 


If you prefer not to construct a concrete base, we have designed two excellent foundation systems that work well with our garden buildings, the Premium RapidGrid and the PremiumPlus Rapid Pad foundations. 


*Please note that the Rapid foundation systems are not available for all models. Please check they are available for the product you are interested in. This can be found in the foundation options section of your chosen product.


Both Rapid Foundation Systems are a cost effective and environmentally friendly alternative to concrete foundations. Generally costing much less than a concrete base would, the Rapid Foundations do not ruin the surrounding soil and need very little soil to be removed compared to if you were laying a concrete base.


The Premium RapidGrid Foundation System is made up of weed control membrane and high quality, heavy duty plastic grids. These grids click together for ease of placement and to help with the rigidity, creating a strong support that will help spread the weight of the building. 
With this system it is better to have reasonably level ground to start off with as you will then need to move less soil in order to level the ground under the grids. Please note that you will need to fill the grids with pea shingle stones, or similar, that you will need to buy from your local builders merchant.


The PremiumPlus Rapid Pad Foundations is designed for even quicker assembly and is also designed for use with uneven ground. As the name suggests this system uses a series of pads to support your building. These pads are made up of plastic grids at the bottom, filled with pea shingle stones (supplied by us with this system), then heavy duty plastic pedestals which screw up and down to adjust in height (giving up to 100mm of variance in height between pads), and also additional bearers with most buildings to reinforce the bearers that are supplied with your garden building which increases the distance that can be spanned between pads. 



The Rapid Systems are also time efficient. You can get your base into place relatively quickly and with little fuss compared to a concrete base. Simply digging down 30-40mm in medium firm ground conditions is perfectly sufficient to hold the building stable. There's no waiting for the base to set and dry, once they're in you're ready to start building.





The Rapid Foundations are designed to work in medium firm ground conditions, and are suitable for the majority of gardens. Please be aware that they are not suitable for areas prone to water logged conditions, marsh, peat or recently disturbed ground. If you are unsure if your ground is suitable for foundations which will exert approx. 17Kpa of pressure, please talk to a local geotechnical engineer prior to purchasing.


Below are examples of ground that is and isn't suitable from a levelling point of view for the Premiumplus RapidPad system. With the Premium RapidGrid system you can level the ground under the grids by moving earth.


This ground is OK

The above diagram shows ground that is within the range of 60mm to 100mm down from the level of the bearers. You may also notice that the ground in between the first and second pedestal is almost at the height of the level shown, this is fine as the bottom of the bearers only starts at the line marked level.


This ground is NOT suitable

The above diagram gives an example of ground which is too uneven. In this example the two extreme extents of the pads adjustability are shown to the right (60mm) and left (160mm) of the diagram but the pads in between are too far below the level and if jacked up to 160mm high they would not reach the level.


This ground is OK


The above diagram shows ground which is sloping but the slope is within the range of adjustability that the pads can cope with. Over the entirety of the length of the ground from one end of the building to the other the height on one side is 60mm from the level, and the height on the other side is up to 160mm from the level so the adjustment available with the RapidPad will be able to cope with this slope.


This ground is NOT suitable 


The above diagram shows a slope that is too steep for the RapidPad foundation system. The distance from the level on one side is 60mm but the height difference between the ground and the level on the other side is too much as it is greater than 160mm.


If your ground conditions are not suitable for the Premium RapidGrid and PremiumPlus RapidPad foundations due to steep slopes or unstable ground then you may find reinforced concrete a better option, as all garden buildings need to be constructed on a flat level surface.


When laying a concrete foundation for your garden building we suggest you add 100mm all the way around the sizes given for the building you have purchased. This will help spread the weight of the building and help ensure that if the base is slightly out of square that the building will still fit on the base, for example:


  • A 4m x 3m building would need a base of approximately 4200mm wide x 3200mm deep
  • For a 4m x 3m building plus a 1.5m veranda the base would need to be approximately 4200mm wide x 4700mm deep
  • For a 9m x 3m building the base would need to be approximately 9200mm wide x 3200mm deep



Please note: Installation is offered on the PremiumPlus RapidPad but not on the Premium RapidGrid.